A Brief Note On Bridges And The Construction Of A Model Spaghetti Bridge

In the small town of Waco, Texas who would have thought it was once well known for the structure of a bridge, the Waco Suspension Bridge to be exact. Up until 1870, the Brazos River was just a simple river that had no special meaning to it. The land around it was empty, occasionally you would find cattlemen pushing their cattle across stream, but that was only because you could not find one bridge that spanned the eight hundred miles of river flowing through Central Texas. This caused a serious transportation issue for merchants and travelers. It became clear that a better means of crossing the river was necessary.

The first example of an external force is the static (dead) load, this refers to the gravitational forces acting on the bridge itself. Every structure has to be able to support the weight of its own materials in order for it not to collapse, this is before any live load is applied to it. Another example is dynamic (live) load which refers to traffic, from people or vehicles, which move across the bridge and apply additional weight to it increasing the magnitude of vertical forces acting on the bridge. But environmental factors such as changes in temperature, precipitation and winds can also create vertical and horizontal loads on the bridge. (Bagga

Initially, suspension bridges before 1940 were made of piers, towers, wires, anchorages, and roadways. Piers were the main foundation for the suspension bridges. There usually were two of them, which were made out of cement and were entrenched in ground underneath the body of water that the bridge was spanned across. Towers were built on top of the piers to provide a means of connection for the roadways and wires. Wires were connected to the towers, roadways, and anchorages to provide tension support for the weight of the bridge. The anchorages were large cement platforms that were planted into the ground on either side of the land so that the wires could be connected to it. Lastly, the roadways were the main point of the suspension bridge. They usually were wide enough to provide four lanes of traffic and stretched from one side of the bridge to the other. This was the basic design of the suspension bridges

Calculations were performed to determine the effectiveness of the design of the platform. Allowing for a safety factor of 1.5 times the design weight of 10kg and considering the bridge must not be overdesigned; plans were made for the bridge to fail at 25kg, 2.5 times that of the design weight. According to the calculations, the bridge would hold a load of over 15kg and experience failure at 20kg in the members. These calculations were later disproven in the testing, breaking 8kg earlier than expected, due to unforseen errors. An analysis of the bridge design and calculations has been included at the end of this report.

The final primary component of a suspension bridge is the deck, or the roadway upon which cars drive and pedestrians walk. The deck is built from massive pieces of steel-reinforced concrete hoisted into the air and laid into place upon the bridge. Deck pieces are connected with bolts and rivets, then suspension cables connect each section of deck to the main

Bridges are a vital part of people’s everyday life and without them people would not be able to do nearly as much as is possible today. The weather in the outer banks of North Carolina is very rough and can be very detrimental to the various structures on them. When hurricanes come near North Carolina the outer banks are hit the worst. Bridges on the outer banks keep being destroyed by weather and so the people there have to think about the cost, the effectiveness, and the need between a strong expensive bridge that will be able to handle rough weather or a cheap quick to build bridges that may fall with any extreme weather.

Several students are doing Science Fair projects at Woodstock Middle School and I am one of the seventh grade students. The topic I shall be doing is on how bridge structure affects the weight bearing capacity. I chose this specific topic to guide bridge builders in the right direction on what bridge is safest for public use. The key topics I plan to research on include the following: Beam, Warren Truss, suspension, cable-stayed, and arch bridges. I shall use the scientific method to guide me through this process.

Clark Eldridge, an engineer from Washington State, had designed a trusted, conventional suspension bridge that would cost eleven million dollars. He requested that amount from the Federal Public Works Administration. However, Leon Moisseiff developed a design modification that would make the total cost of building the bridge much less- only eight million dollars. He swapped out the twenty-five feet long sturdy trusses as the form of support for the much cheaper alternative of 8 foot long girders, which were proven to be an insufficient form of support from the collapse of this bridge. His design accounted for an overall thinner bridge; and since his was the cheaper option, it was chosen for construction. However, the width of the bridge in comparison to the length, as well as the absence of trusses which would provide stability, are both part of Moisseiff’s “cost-effective”, yet impractically unsafe design. Since his design was flawed, he is mainly responsible for the bridge collapse. However, the board of engineers who approved his design are also partially responsible for the bridge collapse, as this unsafe design was allowed to be constructed. Meanwhile, it is imperative to remember that theories on aerodynamics were not fully developed as of the time that this bridge was constructed. Therefore, the full effect of oscillating forces was not properly accounted for due to the

Hecox (2011) says that the arch structure of the Tillman Bridge makes the canyon walls hold the weight of both vehicles and the bridge itself. In addition, the arch structure allows a better vision of the canyon for the drivers, which was a request of the population to the engineers of the project. In the other hand, according to Jones (2015), the truss structure of the new St. Anthony Bridge also was requested by the population because they wanted to keep a truss bridge in that place. The author also affirms that the St. Anthony Bridge is a truss, but the project team proposed adding a posttensioned concrete bottom chord to the steel truss in order to reinforce it. The project team made this choice because one bridge in Minnesota has collapsed in 2007, and the engineers wanted to lessen the fracture-critical issues to avoid a new catastrophe. In addition, this posttensioning approach wiil make the structure redundant for both resiliency and long-term durability. In conclusion, both bridge's structures were right chosen in order to provide safety and beauty in both

The structure of a truss bridge is, by design, large and spanning a large gap. The interconnecting triangular components need to be large to bear and distribute heavy forces applied to the truss. This means in certain conditions (restricted spaces), the truss bridge may not be the best option.

Inhabited bridges are believed to have emerged as a spontaneous occupation of bridges in response to a growing demand of building land in cities and towns which were limited by defensive walls in Medieval Europe. Geographically, it seems

It is shaped in a way to transfer weight to the towers and anchors with its tension (O'Connor, 1971, p. 372). Cables are made of high strength wires spirally bound to form a rope (O'Connor, 1971, p. 372). Vertical cable suspenders that are fastened to the main cables hang the actual roadway. Stiffening girders and trusses are along the side of the bridge to distribute concentrated loads and help to keep the motion of the bridge at a minimum (Troitsky, 1994, p115).

Because of advancements in today’s technology in construction field, many types of bridges are being constructed depending on the requirement and their suitability for the situations.

The choice of a design concept for a bridge foundation is guided by various factors; several of these

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